Method for the preparation of a protein by yeasts using an inducible system, vectors and correspondence transformed strains

A method of preparing a heterologous protein that comprises:

• i) transforming a yeast cell with:
• a) a first DNA fragment encoding said heterologous protein under control of elements providing for expression of said first DNA fragment in yeast, said elements comprising a higher eucaryotic positive transcription control sequence selected from the group consisting of a natural ligand responsive element activating sequence or a variant of a natural ligand responsive element activating sequence which is a palindromic sequence or a repetition of a palindromic sequence and which retains the function of a natural ligand responsive element activating sequence in a test of inducible expression of β-galactosidase in yeast, that is induced by a higher eucaryotic receptor complexed with a ligand, and
• b) a second DNA fragment that is functional in yeast and that encodes said receptor under control of elements providing for expression of said receptor in yeast, wherein said receptor is a natural nuclear receptor selected from the group consisting of receptors for steroids or for retinoids or for thyroid hormones or for vitamin D3, and variants of said receptors which retain the function of said receptors in yeast, wherein said receptor comprises a first fragment that recognizes said ligand and a second fragment that binds to said transcriptional control sequence;
• ii) culturing said transformed yeast cell resulting from step (i) in the presence of said ligand complexed with the said expressed receptor whereby said transcription control sequence is induced and said heterologous protein is thereby produced;
• and
• iii) isolating said heterologous protein.